1. Field of the Invention
This invention relates to human powered or pedal-type vehicles, such as bicycles or tricycles, and more particularly relates to such vehicles having a streamlined shell for reducing wind resistance and improving performance.
2. Description of the Prior Art
Conventional fixed-gear bicycles have been in existence since around the turn of the century. During that time the basic design has changed very little. The only significant improvements have been in the chain/gearing system. The most successful of these improvements has been the now-familiar derailleur gear-changing system. Other improvements include the coaster brake, the multi-ratio planetary hubs, and the elliptical front sprocket. All of these drive train improvements have added to the roadability and cruising capability of the bicycle, culminating in the now conventional multi-geared (typically ten-speed) bike which is an elegant design having a drive mechanism perfected to nearly 95% efficiency.
Because the basic power source of a human powered vehicle is limited, the speed such a vehicle can obtain is a function of the total drag presented at different speeds. The higher the total drag characteristics of the man/machine combination, the more limited the speed.
Total drag on any rolling vehicle is equal to rolling wheel drag plus aero drag. Despite its sophistication in mechanical design, the present conventional design and development have not addressed the problem of aero drag. At best, the conventional bicycle provides a layout of frame, seat and handle bars which calls for the rider to assume a rather severely humped-over position. While this reduces drag to a slight extent, it is also quite uncomfortable and is acceptable only to racers and the more serious cycling afficionados.
With the current trend of increasing scarcity and cost of fuels for vehicle propulsion, it becomes appropriate to seriously consider the feasibility of human powered vehicles as commuting vehicles. However, despite the clear need for such use of human powered vehicles, the commuter field has scarcely been penetrated. While bicycles are more popular now than ever before, they are still used mainly for recreation and exercise. Only a few of the more serious bicycling enthusiasts use such vehicles for commuting to and from work, and then only for short distances of ten miles or less. There is a real need for a breakthrough which will render human powered vehicles more attractive and feasible as commuter vehicles.
The conventional unstreamlined bicycle has a fairly large aerodynamic frontal area and a high drag coefficient. The drag due to wind resistance increases nonlinearly with speed and becomes a substantial limiting factor for the expenditure of less than extreme effort at speeds above 15 or 20 mph. There have been a number of efforts at trying to reduce bicycle/rider wind resistance in order to reduce the effort required to develop better vehicle speeds. Some of the resulting arrangements involve adding a streamlined shell to a bicycle, which has the effect of reducing stability and making the vehicle actually dangerous in cross winds of any noticeable magnitude. Other developments have produced three-wheeled streamlined vehicles in which the rider pedals lying on his stomach with his head forward, a relatively uncomfortable and unsafe arrangement. A suitable combination of rider position, propulsion and wheel arrangement with improved streamlining is needed before a truly acceptable human powered commuter vehicle is realized.